There is widespread use of automatic labelling devices for applying self-adhesive labels of the pressure-sensitive type on a great variety of articles. The labels may be preprinted or printed just prior to application of labels to articles. The self-adhesive pressure-sensitive type of label is usually provided in supply form by locating the labels in a spaced-apart manner on a backing or carrier web. The web is pretreated to ensure ease of separation of label from the backing paper. To provide the supply of labels for the labelling device, such labels as they adhere to the backing are in the form of a roll which may be placed on a supply reel.
An example of an automatic labelling device using such supply of labels is that manufactured by Accraply Systems, a division of Elcono Corporation of Minneapolis, Minn., and sold under the trademark ACCRAPLY. That device applies self-adhesive labels to articles as they are conveyed past the labeller. In that instance, the label is dispensed by passing the carrier web with labels along a ramp sloped relative to the surface to which a label will be applied and pulling the carrier web around the free end of the ramp or splitter tongue to separate the label from the web. This separation is due to the label being stiffer than the carrier web and the optional presence of release agents on the carrier web. The separated label is then applied to an article.
A system has been developed to apply labels to file folders, where a plurality of automatic labellers apply labels at predetermined locations on a file. The system is described in co-pending U.S. patent application Ser. No. 830,118 now U.S. Pat. No. 4,103,779 and Canadian patent application Ser. No. 291,224.
For reasons more fully explained in co-pending United States application Ser. No. 17,966, it is desirable to determine the position of the label which is about to be applied so that missing labels, inconsistent spacing between labels on the carrier web or varying lengths of labels create no problem in the labelling operation. Approaches have been made in the past to sense label position in this manner, such as disclosed in U.S. Pat. No. 3,801,408. Although not specifically defined in that patent, it is presumed that the label sensor operates on the basis of light reflectivity to determine the presence of a label. It is apparent that other approaches include the use of laser scanning device to read marks on a label to determine label position. The provision of marks on the label requires additional steps in printing of the label; therefore, adding to its cost. Should the marks be faulty, there is the resultant inaccuracy in label detection.
It is, therefore, desirable to provide a label sensor which is abosolute in detecting the presence of a label to increase accuracy in the labelling operation. To accomplish this by working within the confines of the compact label splitter tongue of the type which is used to separate labels from carrier web has been a significant problem.
It is, therefore, an object of this invention to provide a label sensor device for labelling apparatus which is capable of accurately determining label presence, at least for a label next to be separated from the web in a compact, easy to manufacture, reliable manner.